[RTT2] Throttle requests from non-foreground apps/services

RTT requests from non-foreground apps/services are throttled to
a low rate (1/30 minutes). Requests received more frequently are
rejected - i.e. not queued.

Bug: 65015291
Test: unit tests and integration tests
Change-Id: Iedaf1b1b21437eceed7e2a55cf76b2df8b3c5fc2
3 files changed